1 const char deanimate_rcs[] = "$Id: deanimate.c,v 1.12 2002/05/12 21:36:29 jongfoster Exp $";
2 /*********************************************************************
4 * File : $Source: /cvsroot/ijbswa/current/deanimate.c,v $
6 * Purpose : Declares functions to deanimate GIF images on the fly.
8 * Functions declared include: gif_deanimate, buf_free,
9 * buf_copy, buf_getbyte, gif_skip_data_block, and
12 * Copyright : Written by and Copyright (C) 2001 by the the SourceForge
13 * Privoxy team. http://www.privoxy.org/
15 * Based on the GIF file format specification (see
16 * http://tronche.com/computer-graphics/gif/gif89a.html)
17 * and ideas from the Image::DeAnim Perl module by
18 * Ken MacFarlane, <ksm+cpan@universal.dca.net>
20 * This program is free software; you can redistribute it
21 * and/or modify it under the terms of the GNU General
22 * Public License as published by the Free Software
23 * Foundation; either version 2 of the License, or (at
24 * your option) any later version.
26 * This program is distributed in the hope that it will
27 * be useful, but WITHOUT ANY WARRANTY; without even the
28 * implied warranty of MERCHANTABILITY or FITNESS FOR A
29 * PARTICULAR PURPOSE. See the GNU General Public
30 * License for more details.
32 * The GNU General Public License should be included with
33 * this file. If not, you can view it at
34 * http://www.gnu.org/copyleft/gpl.html
35 * or write to the Free Software Foundation, Inc., 59
36 * Temple Place - Suite 330, Boston, MA 02111-1307, USA.
39 * $Log: deanimate.c,v $
40 * Revision 1.12 2002/05/12 21:36:29 jongfoster
41 * Correcting function comments
43 * Revision 1.11 2002/03/26 22:29:54 swa
44 * we have a new homepage!
46 * Revision 1.10 2002/03/24 13:25:43 swa
47 * name change related issues
49 * Revision 1.9 2002/03/13 00:27:04 jongfoster
52 * Revision 1.8 2002/03/09 19:42:47 jongfoster
53 * Fixing more warnings
55 * Revision 1.7 2002/03/08 17:46:04 jongfoster
56 * Fixing int/size_t warnings
58 * Revision 1.6 2002/03/07 03:46:17 oes
59 * Fixed compiler warnings
61 * Revision 1.5 2001/09/10 10:16:06 oes
62 * Silenced compiler warnings
64 * Revision 1.4 2001/07/18 12:28:49 oes
65 * - Added feature for extracting the first frame
67 * - Separated image buffer extension into buf_extend
68 * - Extended gif deanimation to GIF87a (untested!)
71 * Revision 1.3 2001/07/15 13:57:50 jongfoster
72 * Adding #includes string.h and miscutil.h
74 * Revision 1.2 2001/07/13 13:46:20 oes
75 * Introduced GIF deanimation feature
78 **********************************************************************/
87 #include "deanimate.h"
90 const char deanimate_h_rcs[] = DEANIMATE_H_VERSION;
92 /*********************************************************************
96 * Description : Safely frees a struct binbuffer
99 * 1 : buf = Pointer to the binbuffer to be freed
103 *********************************************************************/
104 void buf_free(struct binbuffer *buf)
106 if (buf == NULL) return;
108 if (buf->buffer != NULL)
118 /*********************************************************************
120 * Function : buf_extend
122 * Description : Ensure that a given binbuffer can hold a given amount
123 * of bytes, by reallocating its buffer if necessary.
124 * Allocate new mem in chunks of 1024 bytes, so we don't
125 * have to realloc() too often.
128 * 1 : buf = Pointer to the binbuffer
129 * 2 : length = Desired minimum size
132 * Returns : 0 on success, 1 on failiure.
134 *********************************************************************/
135 int buf_extend(struct binbuffer *buf, size_t length)
139 if (buf->offset + length > buf->size)
141 buf->size = ((buf->size + length + (size_t)1023) & ~(size_t)1023);
142 newbuf = (char *)realloc(buf->buffer, buf->size);
151 buf->buffer = newbuf;
160 /*********************************************************************
162 * Function : buf_copy
164 * Description : Safely copies a given amount of bytes from one
165 * struct binbuffer to another, advancing the
166 * offsets appropriately.
169 * 1 : src = Pointer to the source binbuffer
170 * 2 : dst = Pointer to the destination binbuffer
171 * 3 : length = Number of bytes to be copied
173 * Returns : 0 on success, 1 on failiure.
175 *********************************************************************/
176 int buf_copy(struct binbuffer *src, struct binbuffer *dst, size_t length)
180 * Sanity check: Can't copy more data than we have
182 if (src->offset + length > src->size)
188 * Ensure that dst can hold the new data
190 if (buf_extend(dst, length))
196 * Now that it's safe, memcpy() the desired amount of
197 * data from src to dst and adjust the offsets
199 memcpy(dst->buffer + dst->offset, src->buffer + src->offset, length);
200 src->offset += length;
201 dst->offset += length;
208 /*********************************************************************
210 * Function : buf_getbyte
212 * Description : Safely gets a byte from a given binbuffer at a
216 * 1 : src = Pointer to the source binbuffer
217 * 2 : offset = Offset to the desired byte
219 * Returns : The byte on success, or 0 on failiure
221 *********************************************************************/
222 unsigned char buf_getbyte(struct binbuffer *src, size_t offset)
224 if (src->offset + offset < src->size)
226 return (unsigned char)*(src->buffer + src->offset + offset);
236 /*********************************************************************
238 * Function : gif_skip_data_block
240 * Description : Safely advances the offset of a given struct binbuffer
241 * that contains a GIF image and whose offset is
242 * positioned at the start of a data block, behind
246 * 1 : buf = Pointer to the binbuffer
248 * Returns : 0 on success, or 1 on failiure
250 *********************************************************************/
251 int gif_skip_data_block(struct binbuffer *buf)
256 * Data blocks are sequences of chunks, which are headed
257 * by a one-byte length field, with the last chunk having
260 while((c = buf_getbyte(buf, 0)) != '\0')
262 if ((buf->offset += c + 1) >= buf->size - 1)
274 /*********************************************************************
276 * Function : gif_extract_image
278 * Description : Safely extracts an image data block from a given
279 * struct binbuffer that contains a GIF image and whose
280 * offset is positioned at the start of a data block
281 * into a given destination binbuffer.
284 * 1 : src = Pointer to the source binbuffer
285 * 2 : dst = Pointer to the destination binbuffer
287 * Returns : 0 on success, or 1 on failiure
289 *********************************************************************/
290 int gif_extract_image(struct binbuffer *src, struct binbuffer *dst)
295 * Remember the colormap flag and copy the image head
297 c = buf_getbyte(src, 9);
298 if (buf_copy(src, dst, 10))
304 * If the image has a local colormap, copy it.
308 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
313 if (buf_copy(src, dst, 1)) return 1;
316 * Copy the image chunk by chunk.
318 while((c = buf_getbyte(src, 0)) != '\0')
320 if (buf_copy(src, dst, 1 + (size_t) c)) return 1;
322 if (buf_copy(src, dst, 1)) return 1;
325 * Trim and rewind the dst buffer
327 if (NULL == (dst->buffer = (char *)realloc(dst->buffer, dst->offset))) return 1;
328 dst->size = dst->offset;
335 /*********************************************************************
337 * Function : gif_deanimate
339 * Description : Deanimate a given GIF image, i.e. given a GIF with
340 * an (optional) image block and an arbitrary number
341 * of image extension blocks, produce an output GIF with
342 * only one image block that contains the last image
343 * (extenstion) block of the original.
344 * Also strip Comments, Application extenstions, etc.
347 * 1 : src = Pointer to the source binbuffer
348 * 2 : dst = Pointer to the destination binbuffer
349 * 3 : get_first_image = Flag: If set, get the first image
350 * If unset (default), get the last
352 * Returns : 0 on success, or 1 on failiure
354 *********************************************************************/
355 int gif_deanimate(struct binbuffer *src, struct binbuffer *dst, int get_first_image)
358 struct binbuffer *image;
360 if (NULL == src || NULL == dst)
365 c = buf_getbyte(src, 10);
368 * Check & copy GIF header
370 if (strncmp(src->buffer, "GIF89a", 6) && strncmp(src->buffer, "GIF87a", 6))
376 if (buf_copy(src, dst, 13))
383 * Look for global colormap and copy if found.
387 if (buf_copy(src, dst, (size_t) 3 * (1 << ((c & 0x07) + 1))))
394 * Reserve a buffer for the current image block
396 if (NULL == (image = (struct binbuffer *)zalloc(sizeof(*image))))
402 * Parse the GIF block by block and copy the relevant
405 while(src->offset < src->size)
407 switch(buf_getbyte(src, 0))
410 * End-of-GIF Marker: Append current image and return
416 * Image block: Extract to current image buffer.
420 if (gif_extract_image(src, image)) goto failed;
421 if (get_first_image) goto write;
425 * Extension block: Look at next byte and decide
428 switch (buf_getbyte(src, 1))
431 * Image extension: Copy extension header and image
432 * to the current image buffer
436 if (buf_copy(src, image, 8) || buf_getbyte(src, 0) != 0x2c) goto failed;
437 if (gif_extract_image(src, image)) goto failed;
438 if (get_first_image) goto write;
442 * Application extension: Skip
445 if ((src->offset += 14) >= src->size || gif_skip_data_block(src)) goto failed;
449 * Comment extension: Skip
452 if ((src->offset += 2) >= src->size || gif_skip_data_block(src)) goto failed;
456 * Plain text extension: Skip
459 if ((src->offset += 15) >= src->size || gif_skip_data_block(src)) goto failed;
463 * Ooops, what type of extension is that?
471 * Ooops, what type of block is that?
477 } /* -END- while src */
480 * Either we got here by goto, or because the GIF is
481 * bogus and EOF was reached before an end-of-gif marker
490 * Append the current image to dst and return
494 if (buf_copy(image, dst, image->size)) goto failed;
495 if (buf_extend(dst, 1)) goto failed;
496 *(dst->buffer + dst->offset++) = 0x3b;